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41 results on '"Kotrusz, Peter"'

1. Hexatic Phase in Covalent Two-Dimensional Silver Iodide

Author

Bui, Thuy An, Lamprecht, David, Madsen, Jacob, Kurpas, Marcin, Kotrusz, Peter, Markevich, Alexander, Mangler, Clemens, Kotakoski, Jani, Filipovic, Lado, Meyer, Jannik C., Pennycook, Timothy J., Skakalova, Viera, and Mustonen, Kimmo

Subjects
Condensed Matter - Materials Science, Condensed Matter - Disordered Systems and Neural Networks
Abstract

According to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory, the transition from a solid to liquid in two dimensions (2D) proceeds through an orientationally ordered liquid-crystal-like hexatic phase. While experiments have confirmed the KTHNY melting scenario in some 2D systems such as crystals of skyrmions and of noble gas atoms, no evidence has previously been found for it in covalently bonded 2D crystals. Here, 2D crystals of silver iodide embedded in multi-layer graphene are studied with in situ scanning transmission electron microscopy (STEM). Near the melting point, a highly dynamic state of AgI emerges that we show to be the first observation of the hexatic phase in covalent 2D materials.

Published
2025

2. Towards Exotic Layered Materials: 2D Cuprous Iodide

Author

Mustonen, Kimmo, Hofer, Christoph, Kotrusz, Peter, Markevich, Alexander, Hulman, Martin, Mangler, Clemens, Susi, Toma, Pennycook, Timothy J., Hricovini, Karol, Richter, Christine M., Meyer, Jannik C., Kotakoski, Jani, and Skakalova, Viera

Subjects
Condensed Matter - Materials Science, Physics - Computational Physics
Abstract

Heterostructures composed of two-dimensional (2D) materials are already opening many new possibilities in such fields of technology as electronics and magnonics, but far more could be achieved if the number and diversity of 2D materials is increased. So far, only a few dozen 2D crystals have been extracted from materials that exhibit a layered phase in ambient conditions, omitting entirely the large number of layered materials that may exist in other temperatures and pressures. Here, we demonstrate how these structures can be stabilized in 2D van der Waals stacks under room temperature via growing them directly in graphene encapsulation by using graphene oxide as the template material. Specifically, we produce an ambient stable 2D structure of copper and iodine, a material that normally only occurs in layered form at elevated temperatures between 645 and 675 K. Our results establish a route to the production of more exotic phases of materials that would otherwise be difficult or impossible to stabilize for experiments in ambient., Comment: 15 pages, 6 figures, separate supplementary material included

Published
2021
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3. Computational insights and the observation of SiC nanograin assembly: towards 2D silicon carbide

Author

Susi, Toma, Skakalova, Viera, Mittelberger, Andreas, Kotrusz, Peter, Hulman, Martin, Pennycook, Timothy J., Mangler, Clemens, Kotakoski, Jani, and Meyer, Jannik C.

Subjects
Condensed Matter - Materials Science
Abstract

While an increasing number of two-dimensional (2D) materials, including graphene and silicene, have already been realized, others have only been predicted. An interesting example is the two-dimensional form of silicon carbide (2D-SiC). Here, we present an observation of atomically thin and hexagonally bonded nanosized grains of SiC assembling temporarily in graphene oxide pores during an atomic resolution scanning transmission electron microscopy experiment. Even though these small grains do not fully represent the bulk crystal, simulations indicate that their electronic structure already approaches that of 2D-SiC. This is predicted to be flat, but some doubts have remained regarding the preference of Si for sp$^{3}$ hybridization. Exploring a number of corrugated morphologies, we find completely flat 2D-SiC to have the lowest energy. We further compute its phonon dispersion, with a Raman-active transverse optical mode, and estimate the core level binding energies. Finally, we study the chemical reactivity of 2D-SiC, suggesting it is like silicene unstable against molecular absorption or interlayer linking. Nonetheless, it can form stable van der Waals-bonded bilayers with either graphene or hexagonal boron nitride, promising to further enrich the family of two-dimensional materials once bulk synthesis is achieved., Comment: 10 pages, 5 figures, 4 supplementary figures

Published
2017
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5. Electronic Transport in Composites of Graphite Oxide with Carbon Nanotubes

Author

Skakalova, Viera, Vretenar, Viliam, Kopera, Lubomir, Kotrusz, Peter, Mangler, Clemens, Mesko, Marcel, Meyer, Jannik C., and Hulman, Martin

Subjects
Condensed Matter - Materials Science
Abstract

We show that the presence of electrically insulating graphite oxide (GO) within a single wall carbon nanotube network strongly enhances electrical conductivity, whereas reduced graphite oxide, even though electrically conductive, suppresses electrical conductivity within a composite network with single wall carbon nanotubes. Measurements of Young modulus and of Raman spectra strongly support our interpretation of the indirect role of the oxide groups, present in graphite oxide within the single wall carbon nanotubes/graphite oxide composite, through electronic doping of metallic single wall carbon nanotubes.

Published
2013

9. Toward Exotic Layered Materials: 2D Cuprous Iodide

Author

Mustonen, Kimmo, primary, Hofer, Christoph, additional, Kotrusz, Peter, additional, Markevich, Alexander, additional, Hulman, Martin, additional, Mangler, Clemens, additional, Susi, Toma, additional, Pennycook, Timothy J., additional, Hricovini, Karol, additional, Richter, Christine, additional, Meyer, Jannik C., additional, Kotakoski, Jani, additional, and Skákalová, Viera, additional

Published
2022
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10. Polarized Raman Reveals Alignment of Few-Layer MoS2 Films

Author

Hulman, Martin, primary, Sojková, Michaela, additional, Végsö, Karol, additional, Mrkyvkova, Nada, additional, Hagara, Jakub, additional, Hutár, Peter, additional, Kotrusz, Peter, additional, Hudec, Ján, additional, Tokár, Kamil, additional, Majkova, Eva, additional, and Siffalovic, Peter, additional

Published
2019
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11. A comparative life cycle assessment of graphene and activated carbon in a supercapacitor application

Author

European Commission, Álvarez Centeno, Teresa [0000-0001-8405-7298], Cossutta, Matteo, Vretenar, Viliam, Álvarez Centeno, Teresa, Kotrusz, Peter, McKechnie, Jon, Pickering, Stephen J., European Commission, Álvarez Centeno, Teresa [0000-0001-8405-7298], Cossutta, Matteo, Vretenar, Viliam, Álvarez Centeno, Teresa, Kotrusz, Peter, McKechnie, Jon, and Pickering, Stephen J.

Abstract

Graphene shows substantial promise in improving the technical performance of a range of applications. For its development and before its potential mass adoption, it is critical to understand the associated cradle-to-grave life cycle environmental impacts. Previous studies on graphene environmental performance do not include end of life and the potential environmental credits generated by graphene reuse. This study undertakes a cradle-to-grave approach to evaluating graphene applications, considering a case study of supercapacitors manufactured with graphene and activated carbon active materials. The analysis includes active materials commercial-size production, supercapacitors production, supercapacitors use phase in an automotive application, and their end of life in which both devices are recycled. With current material performance and energy mixes, the graphene-based supercapacitor would increase impacts in all environmental categories analysed, ranging from 27% higher human toxicity to 213% greater ozone depletion and showing a 48% increase in GHG emissions. This unfavourable result arises due to the tested graphene material exhibiting inferior specific capacitance to the activated carbon comparator, as well as a more energy-intensive production process. Prospective analysis considers hypothetical performance where both active materials reach their theoretical specific capacitance, and the decarbonisation of electricity generation. The environmental impacts of both the activated carbon and graphene supercapacitors are reduced in these prospective scenarios, with the graphene based supercapacitor becoming the least impacting solution due to its lower active material requirements. The graphene-based device shows 36% lower GHG emission and overall shows lower impacts ranging from 14% less mineral, fossil and renewable resource depletion to 43% less photochemical ozone formation. These results support graphene as a valid candidate material for substituting activated

Published
2019

12. Biomass waste-carbon/reduced graphene oxide composite electrodes for enhanced supercapacitors

Author

Consejo Superior de Investigaciones Científicas (España), Álvarez Centeno, Teresa [0000-0001-8405-7298], Guardia, Laura, Suárez Fernández, Loreto, Querejeta Montes, Nausika, Vretenár, Viliam, Kotrusz, Peter, Skákalová, Viera, Álvarez Centeno, Teresa, Consejo Superior de Investigaciones Científicas (España), Álvarez Centeno, Teresa [0000-0001-8405-7298], Guardia, Laura, Suárez Fernández, Loreto, Querejeta Montes, Nausika, Vretenár, Viliam, Kotrusz, Peter, Skákalová, Viera, and Álvarez Centeno, Teresa

Abstract

We present a simple and effective alternative which optimizes electrodes based on low-cost carbons for high-performance supercapacitors. The combination with reduced graphene oxide (rGO) greatly improves the operation of microporous carbons easily produced by one-pot activation of grape seeds. The use of composite electrodes with rGO lowers the supercapacitor resistance and enables a much higher rate capability. The mixture of rGO flakes and particles of a highly porous carbon obtained by KOH activation allows retaining the high capacitance of 260 F g−1 of the standard electrodes at 1 mA cm−2 in aqueous H2SO4 whereas the value at 200 mA cm−2 is increased by around 2.4 times. Consequently, at high current density, the capacitor assembled with these composites stores eight times more energy and the power density is multiplied by four. The synergy between rGO and an ultramicroporous carbon produced by CO2-activation results extremely profitable, the cell assembled with composite electrodes reaching three times more energy and power at 200 mA cm−2 than the best performance of the standard counterpart. More importantly, the higher density of the composite electrodes leads to a capacitance of around 200 F cm−3 which translates into a remarkable improvement in the supercapacitor operation normalized to volume.

Published
2018

17. Chemical Oxidation of Graphite: Evolution of the Structure and Properties

Author

Skákalová, Viera, Kotrusz, Peter, Jergel, Matej, Susi, Toma, Mittelberger, Andreas, Vretenár, Viliam, Šiffalovič, Peter, Kotakoski, Jani, Meyer, Jannik C., and Hulman, Martin

Abstract

Graphene oxide is a complex material whose synthesis is still incompletely understood. To study the time evolution of structural and chemical properties of oxidized graphite, samples at different temporal stages of oxidation were selected and characterized through a number of techniques: X-ray photoelectron spectroscopy for the content and bonding of oxygen, X-ray diffraction for the level of intercalation, Raman spectroscopy for the detection of structural changes, electrical resistivity measurements for probing charge localization on the macroscopic scale, and scanning transmission electron microscopy for the atomic structure of the graphene oxide flakes. We found a nonlinear behavior of oxygen uptake with time where two concentration plateaus were identified: Uptake reached 20 at % in the first 15 min, and after 1 h a second uptake started, reaching a highest oxygen concentration of >30 at % after 2 h of oxidation. At the same time, the interlayer distance expanded to more than twice the value of graphite and the electrical resistivity increased by seven orders of magnitude. After 4 days of chemical processing, the expanded structure of graphite oxide became unstable and spontaneously exfoliated; more than 2 weeks resulted in a significant decrease in the oxygen content accompanied by reaggregation of the GO sheets. These correlated measurements allow us to offer a comprehensive view into the complex oxidation process.

Published
2024
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19. Highly enantioselective addition of Me2Zn to aldehydes catalyzed by ClCr(Salen)

Author

Cozzi, Pier Giorgio and Kotrusz, Peter

Subjects
Aldehydes -- Chemical properties, Zinc compounds -- Chemical properties, Enantiomers -- Chemical properties, Chemistry
Abstract

A highly efficient catalytic asymmetric addition of Me2Zn to aldehydes promoted by a chiral Cr(Salen) meta complex is described. While different metal Salen complexes did not produce a reaction after 24 h, 2% of commercially available ClCr(Salen) was able to promote the addition of Me2Zn at room temperature, and a remarkable enantiomic excess of 97% was obtained in this model reaction.

Published
2006

36. Highly Efficient MolybdenumIICatalyzed Intramolecular Allylic Alkylation of Arenes

Author

Bandini, Marco, Eichholzer, Astrid, Kotrusz, Peter, and UmaniRonchi, Achille

Abstract

The Friedel–Craftstype intramolecular allylic alkylation of simple arenes is performed in the presence of a catalytic amount of MoII CO4Br222.5 mol%. The moisturetolerant protocol provided a mild and direct access to a large library of functionalized 4vinyl1,2,3,4tetrahydronaphthalenes in high yields.

Published
2008
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37. Michael Additions of Aldehydes and Ketones to β-Nitrostyrenes in an Ionic Liquid

Author

Kotrusz, Peter, Toma, Stefan, Schmalz, Hans-Günther, and Adler, Andreas

Abstract

Michael additions of different aldehydes and ketones to β-nitrostyrene and 2-(β-nitrovinyl)thiophene in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) were studied. β-Nitrostyrene was a better acceptor than 2-(β-nitrovinyl)thiophene, in terms of both reactivity and selectivity. Aldehydes proved to be better donors than ketones, which were themselves better than β-diketones. L-proline proved to be the best catalyst among seven organocatalysts tested. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Published
2004
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40. Michael addition of thiols to alpha-enones in ionic liquids with and without organocatalysts.

Author

Meciarová M, Toma S, and Kotrusz P

Subjects
Catalysis, Cycloparaffins chemical synthesis, Hydrocarbons, Chlorinated chemistry, Kinetics, Magnetic Resonance Spectroscopy, Models, Molecular, Solvents, Cycloparaffins chemistry, Organic Chemicals chemistry, Sulfhydryl Compounds chemistry
Abstract

Seventeen organocatalyts were tested for their ability to catalyst the addition of thiophenols to chalcones in [bmim]PF6. The products were isolated in high yield after a short reaction time, but no stereoselectivity was observed. The reactions also proceeded (without any stereoselectivity) in four other ionic liquids. In contrast, 16% and 26% ee were observed when L-proline and cinchonine, respectively, were used as the catalysts in CH2Cl2. Addition of thiophenols is also catalysed by HCl, as well as D-mandelic and L-tartaric acids. Addition of thiophenols to chalcones also occurred in neat ionic liquids, without any additional catalyst, but the rate of the reaction depended considerably on the structure of ionic liquid. The scope of the non-catalysed reaction in ionic liquids was tested by the reactions of 5 different thiols and 3 different alpha-enones.

Published
2006
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41. L-proline catalyzed Michael additions of thiophenols to alpha,beta-unsaturated compounds, particularly alpha-enones, in the ionic liquid [bmim]PF6.

Author

Kotrusz P and Toma S

Subjects
Catalysis, Cycloparaffins chemical synthesis, Kinetics, Magnetic Resonance Spectroscopy, Models, Molecular, Molecular Structure, Solvents, Cycloparaffins chemistry, Ionic Liquids, Organic Chemicals chemistry, Phenols chemistry, Proline chemistry, Sulfhydryl Compounds chemistry
Abstract

L-proline catalyzed additions of 13 different thiols to 11 different alpha-enone Michael acceptors in [bmim] PF(6 )are reported. Reasonable to high yields of the reaction products were isolated in most cases.

Published
2006
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